The msvc-14.0 toolset seems to be working. Boost.Config is updated. BOOST_MSVC_ENABLE_2014_JUN_CTP must be defined to get the newly added features.
I'd like to encourage someone to start running regular msvc-14.0 regression tests on the develop branch. If there are compiler bugs that affect Boost libraries, reporting them now increases the chance they will be fixed in the actual 2015 release. Microsoft appears to commit more resources to bug fixes in the pre-release run-up than at other times.